Su-Keun Eom

A Compact 30-W AlGaN/GaN HEMTs on Silicon Substrate With Output Power Density of 8.1 W/mm at 8 GHz

A 29.4-W X-band high-power amplifier has been substantialized using GaN on high-resistive silicon substrate. The developed GaN high electron mobility transistor (HEMT) with 3.6-mm gate periphery provides 29.4-W output power and 8-dB small signal gain at 8 GHz with power added efficiency of 39.4% under pulse condition at a duty of 10% with a pulsewidth 100 μs. Load-pull measurement at 8 GHz demonstrates an output power density of 8.1 W/mm. To the best of our knowledge, the presented amplifier exhibits the highest power density, delivering >10 W of output power in X-band for GaN HEMTs technology on silicon substrate.

V-band monolithic microwave integrated circuit with continuous wave output power of >23.5 dBm using conventional AlGaN/GaN-on-Si structure

This letter reports an AlGaN/GaN-on-Si power amplifier (PA) monolithic microwave integrated circuit (MMIC) operating at V-band using advanced gate processing technology. The AlGaN/GaN-on-Si high electron mobility transistors (HEMTs) employed a gate length of 100 nm with a double-deck shaped (DDS) field-plate, which resulted in a cut-off frequency of 68 GHz and a maximum oscillation frequency of 160 GHz at the drain voltage of 15 V with significant reduction in gate resistance and improvement of current collapse phenomenon. A 60 GHz three-stage PA MMIC composed of two 4 × 37 μm and an 8 × 37 μm AlGaN/GaN-on-Si HEMTs successfully demonstrated using the DDS field-plate gate technology, which exhibited a continuous wave output power of >23.5 dBm at the drain voltage of 18 V at 58 GHz. This is the highest output power performance for V-band power amplification based on AlGaN/GaN-on-Si technology.

Thermal stability and small-signal characteristics of AlGaN/GaN HEMTs with gate insertion metal layer for millimeter-wave applications

The effect that insertion gate metals have on GaN millimeter-wave devices undergoing a postmetallization annealing (PMA) process was investigated. It was found that the PMA process increases the gate resistance (Rg), which is responsible for a decrease in the maximum oscillation frequency (fmax). The resistance was examined as a function of line patterns containing various gate metal stacks, including Ni/Au and Ni/Mo/Au, before and after annealing from a low temperature to 550 °C. The metal stack with an Mo insertion layer effectively suppressed Au diffusion into GaN and reduced the increase in the gate metal resistance. For the fabricated AlGaN/GaN-on-Si high-electron-mobility transistors with a Ni/Mo/Au gate, stable gate reliability, improved current collapse characteristics, and small-signal characteristics were also achieved compared to those of the Ni/Au gate.